Who Was Leonardo da Vinci? Painter, Engineer and Compulsive Notebook Keeper

Born in 1452 near Vinci in Tuscany, the illegitimate son of a notary and a peasant woman, he received no formal education in Latin or mathematics, a gap he resented and filled later by teaching himself. At about fourteen he entered the workshop of Andrea del Verrocchio in Florence, where he learned painting, sculpture, metalwork and engineering, all of which a workshop of that period handled. In 1482 he moved to Milan and spent seventeen years in the service of Ludovico Sforza, chiefly as an engineer and organiser of court entertainments, painting the Last Supper and the Virgin of the Rocks in that time. The French invasion of 1499 sent him back to Florence, where he worked briefly as a military engineer for Cesare Borgia, and where he and Michelangelo were commissioned to paint opposing walls of the same hall, a contest neither finished. He spent his final years in France under the patronage of Francis I, dying at Amboise in 1519.

The output is tiny and its influence disproportionate. The Last Supper, painted in Milan between 1495 and 1498, reorganised the subject by catching the moment immediately after the announcement of a betrayal, with the twelve apostles arranged in four groups reacting; it began deteriorating within twenty years because he experimented with painting in tempera on dry plaster rather than in true fresco, and what survives is heavily restored. The Mona Lisa, begun around 1503 and still with him at his death, is famous partly for reasons unrelated to its quality, having been stolen from the Louvre in 1911 and recovered two years later, an episode that made it front-page news across the world. What both show technically is sfumato, his method of building form from many translucent glazes with no visible line anywhere, so that edges dissolve into shadow, which is the opposite of the sharp contour Florentine training taught and is why his faces seem to change expression as you look.

The private work is the larger achievement and was invisible for centuries. He wrote in mirror script, right to left, probably because he was left-handed and it avoided smudging rather than for secrecy, and filled the pages with drawings and observations across an implausible range:

• •Anatomy, including the first accurate drawings of the human spine and skull, a cast of the ventricles of a brain made by injecting wax, and a study of the aortic valve whose account of blood flow was confirmed only in the twentieth century
• •Water, which obsessed him, with hundreds of studies of turbulence, waves, erosion and canal design
• •Flight, including studies of bird wings, a design for a parachute that was built and successfully tested in 2000, and the ornithopter and helical screw devices that everyone reproduces
• •Military engineering, including a tank, a multi-barrelled gun and fortification designs, mostly produced to persuade patrons to employ him
• •Geology, where he correctly deduced from fossil shells high in the mountains that the rock had once been sea floor, against the flood explanation of his day
• •Optics, botany, the proportions of the human figure, the mechanics of gears, and page after page of unrelated observations, shopping lists and reminders

The abandonment is as characteristic as the achievement. A bronze horse for the Sforza family, planned at over seven metres, consumed years of preparation before the metal was requisitioned for cannon. The Battle of Anghiari mural was abandoned after an experimental technique failed to dry. Commissions were taken and not delivered, and a contemporary complained that he could not bear the brush. The explanation usually offered is that his interest was in the problem rather than the object: once he had understood how light falls on a curved surface or how a muscle attaches, the finished panel was an administrative task. His patrons found this maddening, and Vasari, writing thirty years after his death, noted that his knowledge of so many things prevented him from completing any of them. It also meant that almost none of his scientific work entered circulation, since publishing required organising the notes into a treatise, which he repeatedly planned and never did.

He left everything to his pupil Francesco Melzi, who preserved the papers carefully; Melzi's heirs did not, and the collection was broken up, sold, given away and partly lost over the following century. What survives, perhaps a third of the original, is scattered across the Royal Collection at Windsor, the Institut de France, the Ambrosian Library in Milan, Madrid, and one volume bought by Bill Gates in 1994. Serious study began only in the nineteenth century, and the consequence is that his scientific work influenced nobody at the time: the anatomy was rediscovered after Vesalius had published the same findings, and the engineering designs were historical curiosities by the time anyone read them. The modern reputation as the universal genius therefore rests on a body of work that had almost no effect on the fields it anticipated, which is an unusual basis for fame and does nothing to diminish it.

The Tuscan painter trained in Verrocchio's Florentine workshop spent seventeen years as a court engineer in Milan and finished around fifteen paintings in fifty years, of which the Last Supper began decaying almost at once because of an experimental technique. His method of building form from translucent glazes with no visible outline is what gives his faces their instability. The seven thousand surviving pages of mirror-written notes cover anatomy, water, flight, geology and optics at a level unmatched for centuries, and were scattered and unread until the nineteenth century.